In this work, by exploiting Malignant Pleural Mesothelioma as an experimental model of tumor chemoresistance [4, 41], we demonstrated that a specific ALDH isoform, namely ALDH1A3, is enriched in chemoresistant mesothelioma cell subpopulations purified from multiple sources. The gene discussed is ALDH1A3; the disease is mesothelioma.